1. Field of the Invention
The present invention pertains to visual bore hole logging. The visual examination of the bore hole for casing damage and/or fracturing and sediment stratification may be made with a video camera lowered throughout the bore hole and a video monitor in conjunction with a video cassette recorder for visualizing and recording the wall of the bore hole.
2. Description of the Prior Art
A well or bore hole is an artificial excavation made to extract water, oil, gas, and other substances from the earth. There is also the boring and drilling of holes for exploraton. Exploration holes are drilled to locate mineral deposits such as oil and gas, ground water, geothermal supplies, to check for the integrity for nuclear waste depositories, and also to deterine potential landslides in an unstable environment. Close circuit TV camera systems are known in the art for visually examining the walls to a given bore hole. Additionally, in large diameter bore holes, a trained geologist can be physically lowered into the hole with a light source to visually examine the stratification, fracturing and layering of the various geological formations down to which the bore hole penetrates. In small diameter holes, this type examination is impossible. Accordingly, in smaller holes visual wall examination must be made with a moving picture bore hole camera or with a closed circuit television video camera.
Additionally, the bore shaft itself made by the bore hole is often not in a vertical orientation and has a drift or deviation in azimuth from its true vertical. There are drift recorders which monitor and log the slanting or drifting of the bore hole from its true azimuth. Inclinometers are known which determine deviation as well as drift, for exmaple, by phographing from a plumb bob position against a compass background.
Additionally, while in the process of drilling a well and/or installing the steel tubing or casing to reinforce the wall of the bore hole, occasionally because of cave-ins, sedimentation and the like, the equipment in the hole becomes lodged and stuck therein. It then becomes a matter of locating the stuck pipe or other equipment in the wells, U.S. Pat. No. 2,817,808 to Giske, describes a method and apparatus for locating stuck pipe in wells.
After the steel casing or tubing has been in place for sometime in a well such as a ground water well, rusting and other shifts in the earth occasionally will cause rupturing or uncoupling of the steel casing. In this event, visual examination of the casing is necessary to see the extent of the break or leak and the feasibility of repairs.
Accordingly, the visual examination of the walls of a well are frequently needed when applied to the above problems. cl SUMMARY AND OPERATION OF THE INVENTION
An apparatus and method of visually examining the sidewalls of a bore hole include a down hole video tool lowered into the bore hole by means of a cable and winch on the surface. The apparatus includes a wide angle video camera enclosed in its lower section. An upper section houses a power supply/triplexer, a telemetry board, an FM modulator video amplifier transmission board, gyro data interface board and a gyroscope for showing the directional orientation of the camera and apparatus in the bore hole. The gyroscope orientation and the visual image of the portion of the sidewall viewed is transmitted to a video display monitor in an equipment van on the surface. The image on the screen includes a directional reference point so that the direction of a portion of the sidewall being viewed can be ascertained. The camera images are recorded by a video cassette recorder for a permanent record of the visualization of the entire length of the bore hole. Various geological data can be extrapolated by this visualization by means of the observed fracturing and stratification which may be observed in a given bore hole. Additionally, the probe can be used to inspect bore holes previously encased by steel tubing to detect any leaks or other deterioration in the tubing system.
The present invention consists of a down hole video tool which includes an elongate, two-section cylindrical housing which is lowered into the bore hole. The lower end of the tool holds a video camera, a wide angle video camera lens and a light source extending a few feet in front of the lens or around the lens to illuminate the dark interior of the bore hole. There is supportive equipment above ground which includes a winch having a cable attached to the upper end of the tool to lower and retrieve the tool in the well bore. The cable includes a bidirectional data transmitting cable and also an electric cable for providing a power supply to the tool itself. Typically, the winch is installed in a large equipment van used to transport the down hole video tool. Inside the van is a variety of support equipment including a television video monitor, a video cassette recorder, a video printer, telemetry equipment and a computer. A depth measuring device to indicate the position of the tool in the ground, and a temperature sensor to measure the ambient temperature at the location of the tool are also part of the equipment.
The down hole video tool has a pressure resistant housing which houses a video camera, a light source, bidirectional telemetry circuit board for handling and processing the signals for transmittal up to the television/video monitor above ground, video amplification means of the signals, a power supply/triplexer, and a gyro and/or inclinometer.
As the down hole video tool is lowered into the bore hole, it is impossible to keep the camera and tool oriented in one direction. There will always be a twisting or rotational effect by the down hole video tool as it twists on the supporting cable to some extent. As a result, the operator does not know the direction of a side of the wall being visualized on the video monitor by means of the images telemetered from the video camera in the hole. He is unable to tell the orientation or directional bearing of the camera in the hole, i.e., the operator cannot determine the north, south, east or west side of the bore hole displayed on the video monitor.
The present invention incorporates a built-in free gyroscope in the housing which is about one and one-half inches in diameter and is arbitrarily selected to point north and then is "locked in" to always point north. The probe and camera (down hole video tool) can rotate on the cable but the spin axis of the gyro remains fixed in space. A reference point generated by the free gyro is displayed on the video screen to always indicate the directional orientation of the sides of the wall of the hole. The visual display on the video monitor screen will probably show the directional reference point drifting or floating around on the screen as the video camera in the housing rotates back and forth in the bore hole. The camera is stationary in the tool. Directional orientation of the camera is indicated by the signal generated by the built-in gyro. The gyro generates a real time image dot displayed on the video screen above ground. The image dot is self correcting to constantly show target heading of the camera, for directional reference of fractures, bed dip, casing damage or other objects being viewed.
Video logs for the bore hole video examination are visually recorded on three-quarter inch video cassettes for a permanent record. These may then be copied onto VHF, Beta, or other formats for convenience. Also available in the equipment van are hard copies of video images produced by a video printer for immediate presentation, and a video typewriter for recorded commentary. The commentary is recorded on the videotape. The orientation has applications to show hard rock fracture sizing and orientation. For example, the layer of the fracturing can be visually observed and measured by the image on the video screen. If the fracture is inclined, then the angle of inclination can also be extrapolated by a standard trigonometric function by knowing the diameter of the bore, and the difference in height between the top of the fracture at one side of the bore hole and the top of the fracture at the opposite side of the bore hole. The difference in height would form the vertical leg of a right triangle and the diameter would be the horizontal leg of the right triangle. These two numbers could be used to calculate the tangent to find the angle of inclination of the fracture at that particular depth. The reference point showing the true north on the video display monitor would also show the direction of the slope of the fracture line, or bed dip.
The above ground winch which lowers the cable into the well bore hole has an optical encoder and a calibrated wheel on the winch. This measuring equipment displays on the video monitor the depth of the probe within a tenth of a foot. For example, in an average 8 inch diameter hole, the difference in height in the top of the fracture on opposite sides of the hole is three to eight inches. This can easily be determined by looking at the depth reading presented on the video screen at the top of the fracture while the tool is being lowered to the top of the fracture on the other side of the hole and noting or reading the difference in the depth, usually in inches, as shown on the visual display. The acetate overlay showing the compass readings can be overlaid on the screen by placing the center of the graphic compass with the depth reading dot and aligning the north direction point on the screen with the North arrow of the graphic compass and then determining the sloping direction of the fracture and the bed depth. The sloping direction requires two compass readings; one at the top of the fracture having the shallower depth, and the other at the top of the same fracture having the deeper depth.
One could drill an array of exploration bore holes in a given surface area and then map the fractures and stratifications of the underground formations to determine the geological makeup of that given area. In the event where the bore holes are slightly inclined, then the readings from a previously inserted inclinometer could be used as a factor to determine the true angle of inclination of the layers. Or an inclinometer could be used by attaching it to the tool so that all readings could be taken simultaneously.
Accordingly, it is an object of this invention to have a down hole video tool for passing through the length of a drilled bore hole, and having a video camera for visually observing the walls of the bore hole, and in conjunction with a gyroscope in the tool so that the orientation of the camera lens will be known when the data is telemetered up to the video screen monitor in the equipment van so that one will be able to have a directional reference point on the video monitor screen to known the directional orientation shown of the bore hole walls when viewed on the video monitor. The directional reference point provides further data so that one can observe and calculate the rising or dropping angle of any fragmentation of layered rock in the bore hole. The directional indicator also informs one of the direction of leakage in a cased bore hole.
In is an additional object of this invention to provide a video camera and wide angled camera lens attached to the lower end of a down hole video tool and having a light source attached adjacent to the video camera so that the wall of the bore hole can be visually observed and recorded on video tape by means of transmitting the image received by the camera lens and visually displaying it on a video screen while simultaneously recording the visualization of the walls of the bore hole. The video screen also displays data such as the temperature gradient at the video camera and also the depth at the camera so that one can match the visualizations and the layering found in the bore hole with the depth of the camera lens at a particular location.
It is a further object of this invention to provide a down hole video tool having two sections and which is lowered into the bore hole. The tool includes a video camera with wide angle lens in a cylindrical housing forming the lower head section, and an upper section including a cylindrical housing for a power supply/triplexer to power the components, a free gyroscope to indicate the designated reference point of the camera lens, a means for video transmission of the data up to the video display monitor and a telemetry board for handling all of the data inputs and power sources to bidirectionally transmit the data to the surface. These are part of the second section of the tool.